No tablet as exists today are incapable of taking good usable notes, or if they are (Microsoft OneNote running on a Samsung Series 7 with Windows 7) then they certainly won't exceed a regular laptop with a keyboard. People love to claim the technology is up to that stage but as someone who has foolishly wasted more money that I would like to admit on the tablet dream, I can tell you that, no, you're just wasting money.
The "main issue" I've found is two things, first off handwriting recognition is crap. Secondly that even when it works there isn't any real integration with the rest of the system, so the resulting text and diagrams is an uncategorised orphan unusable by anything of use.
Android and iOS are great consumers of content but they're terrible producers. The software is lacking, the interface designs are arse-backwards, and all it ultimately results in is an inefficient irritating system that you might have well not use. Things like the Android Transformer almost prove my point for me by opting for a keyboard and Microsoft Word-clone like software to increase your productivity. If the fact that the best Android can do is to copy a "normal" laptop then that is as damning of a statement of the state of tablets as I can tell.